PROJECT SUMMARY/ABSTRACT There is an urgent need for interventions to reduce mobility limitations that affect over 15 million older adults and contribute to falls, disability, hospitalization and death. This K01 award will build upon Dr. James' expertise in motor control with training in geriatric rehabilitation, mobility intervention development, statistical methods and the conduct of randomized controlled trials. This training will give Dr. James the skills to become an independent researcher developing interventions to decrease mobility limitations, disability and falls in older adults. His multidisciplinary mentorship team, led by Jonathan Bean, MD, MPH (K24HD070966), has extensive experience with NIH sponsored research, expertise in the targeted training domains, mentoring new investigators, and is highly committed to Dr. James' development as a researcher. Dr. James has identified novel impairments in rhythmic interlimb and gait coordination as strongly linked to mobility among community-dwelling older adults. Currently, no treatment for limb coordination exists. Thus, there is a great need to develop feasible, efficacious and safe rehabilitative interventions that address limb coordination impairments and mobility limitations. In an effort to advance the development of treatments for mobility limitations, the objective of the proposed research is to examine the dose-response of an innovative intervention to improve coordination in community-dwelling older adults with mobility limitations. The intervention uses a metronome to retrain coordination impairments that develop with age, and consists of practice improving the coordination of the right and left: a) ankles; b) shoulders; and c) ankles and shoulders, while lying supine, and d) the arms and legs during walking; by synchronizing movements with a metronome. This project is innovative in that it will be the first to examine an intervention for interlimb and gait coordination in older adults with mobility limitations. This project is significant in that the approach may offer a cost-effective, clinically applicable, and efficacious means of reducing mobility limitations in older adults. We will initially refine the intervention, and subsequently conduct a randomized trial of 2-, 4- and 8-week intervention treatments vs. physical activity control with (N=120) community-dwelling older adults aged >70 years with mobility limitations. These treatment durations correspond to what rehabilitative care providers would consider a short vs. medium vs. long duration (dose) of treatment. We will examine the magnitude and duration of change in interlimb ankle coordination and gait coordination for each group. We will estimate the coordination effect sizes for a minimal clinically important difference in mobility performance, and explore changes in upper limb coordination and performance-based and self-reported mobility. This project will lead to a randomized trial examining the intervention effects on changes in mobility.